Siemens SITRANS WM300 MFA Operating Instructions Manual page 68

Technical Reference
A.1 Principles of Operation
The relationship between speed and gap of a standard probe
①
Fig. a
②
Fig. b
③
Fig. c
The resultant line indicates the threshold tolerance of the accompanying SITRANS WM300
MFA electronics. For example, in Fig. a, a 100 mm (4 inch) gap requires a minimum velocity
of about 10 m/minute (35 ft/minute): with a velocity of 0.61 m/minute (2 ft/minute), a
maximum gap of 31 mm (1.25 inch) is possible.
Note
25.4 mm = 1 inch and 0.305 m = 1 ft
68
SITRANS WM300 MFA
Operating Instructions, 08/2018, A5E45090709-AA